★ Stable magnetite nanofluids of various concentrations are synthesized. ★ Magnetic properties are studied and the ultrasonic parameters are estimated. ★ Acoustic response of the fluids to concentration and magnetic field is studied. ★ The temperature effect is explained using open and close packed structures of water. ★ Ultrasonic method is effectively used to explain the cluster formation.
Magnetite nanofluids of various concentrations have been prepared through co-precipitation method. The structural and magnetic properties of the magnetic nanofluids have been analyzed which respectively revealed their face centered cubic crystal structure and super paramagnetic behavior. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. Open- and close-packed water structure is considered to explain the temperature effects. The inter particle interactions of surface modified nanomagnetite particle and the cluster formation are realized through the variations in ultrasonic parameters.